The present invention relates to an etching device, for example, the etching device used for manufacturing a thin film transistor liquid crystal display (TFT-LCD). Take the etching device used for manufacturing the TFT-LCD as an example, the etching device comprises a storage tank, an inlet chamber, an air knife, a shower, a sample, a sensor, a heating means, a rinse means, and an etching chamber, etc.
The etching chamber is the main location for etching reaction. The etching chamber comprises a first etching chamber, a second etching chamber and a third etching chamber. Wherein, the majority of etching reaction is occurred in the first etching chamber for removing the main film in an etching sample; and then the etching sample is transferred into the second etching chamber for cleaning the residual film of the sample; finally the profile of the pattern is mainly formed in the third etching chamber. The chemical reagents employed in the three etching chamber are the same and are applied by two storage tanks disposed beneath. But the consumption speed of the reagent in the first etching chamber is relative more rapid than those in the second and third etching chambers. The chemical reagent undergone the reaction is flowed back into the storage tanks for reusing, and the chemical reagent should be periodically replaced after it is used for a period of time.
FIG. 1 and FIG. 2 schematically illustrate the first etching chamber of the etching device in prior art in a simplified way. FIG. 1 shows a top view, and FIG. 2 shows a side view. As shown in FIG. 1 and FIG. 2, a substrate 5 is transferred into the etching cavity by a transmission apparatus, such that rolling wheels 7. In this case, the substrate 5 is located between an upper substrate 8 and a lower substrate 9 of the etching device, and the etchant sprayed by the nozzles 4 is in contact with the substrate 5 for etching. In prior art, whether the etching is finished that is judged by visual observation, namely the etching time is detected by human eyes (as arrow shown in FIG. 2). When the etchant that has not been reacted is nearly clear with high transmittance. After the substrate 5 is transferred into the etching chamber by the rolling wheels, the etchant is in contact with the substrate and the etching reaction is started, at this time, the etchant becomes turbid and the transmittance is decreased. Simultaneously, the operator starts timing using a stopwatch until the etching reaction is nearly finished and the etchant become clear again, the timing is ended. The period from the time when the etchant becomes turbid to the time when the etchant turns to clear again is defined as the etching time.
The etching time is an important parameter for the subsequent processes. If the detected etching time is shorter than the actual etching time, the residual will be remained after the etching process. If the detected etching time is longer than the actual etching time, an over etching will be occurred. Therefore, the accuracy of detecting the etching time is the most important. As mentioned above, detecting the etching time by visual observation in prior art is not only difficult to achieve an accurate etching time, but also dangerous in operation.